JP2020061383A - Battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of manufacturing an assembled battery having an accurate size. A method for manufacturing an assembled battery provided by the present invention includes a step of preparing a plurality of unit cells each including an electrode body having a positive electrode and a negative electrode, and a container accommodating the electrode body, and a plurality of unit cells. A step of classifying into a plurality of thickness ranks according to the thickness in the arrangement direction of the electrode bodies housed in the unit cells, and arranging a predetermined number of the unit cells in the arrangement direction and applying a load in the arrangement direction Constructing the battery pack by restraining it in a state. In the process of constructing the assembled battery, the length in the arrangement direction of the assembled battery is determined by selecting and combining a predetermined number of unit cells used for constructing the assembled battery from two or more thickness ranks of the plurality of classified thickness ranks. It is done to fit the specified length. [Selection diagram] Fig. 5

Description

  The present invention relates to a method for manufacturing an assembled battery in which a plurality of rechargeable single cells (secondary batteries) are arranged in a predetermined direction and are constrained in a state in which a load is applied in the arrangement direction.

  A lithium-ion secondary battery, a nickel-metal hydride battery or other secondary battery that can obtain a high energy density and a storage element such as a secondary battery or a capacitor is used as a single battery, and a battery pack formed by connecting a plurality of such single batteries in series can obtain high output. It is preferably used as a power supply for vehicles, or as a power supply for personal computers and mobile terminals. For example, in Patent Document 1 as an example of a vehicle-mounted assembled battery, a plurality of cells of the same shape made of a lithium ion secondary battery are arranged, and a positive electrode terminal and a negative electrode terminal provided in each single battery are connected in series. There is disclosed an assembled battery configured by doing the above.

JP, 2014-137889, A

  By the way, an assembled battery mounted on a vehicle such as an automobile is required to be used in a state where vibration is generated in addition to a limited mounting space. Therefore, it is also described in Patent Document 1, for example. As described above, an assembled battery is constructed in which a large number of cells are arranged and restrained (that is, the cells are fixed to each other). At the time of such restraint, a considerable load is applied to each unit cell that constitutes the assembled battery.

According to the knowledge obtained by the present inventor, when a plurality of cells are arranged and restrained by applying a load in the arrangement direction in manufacturing the assembled battery, the container of the single cell (that is, the electrode body is housed inside by the load) Distortion or deformation occurs in the load direction. Therefore, the thickness of each unit cell in the arrangement direction when the load is restrained by applying a load in the predetermined arrangement direction depends on the thickness of the electrode body inside the container.
However, generally, the thickness of the electrode body varies (is uneven) to some extent. When a large number of cells with electrode bodies having variations in thickness are arranged and constrained in the stacking direction, the thickness of the constrained cells in the arrangement direction varies, resulting in variations in the thickness of those cells. As a result, the lengths of the obtained assembled batteries in the arrangement direction vary. Such variations in the arrangement direction length (outer size) of the battery pack may not fit in the mounting space prepared in advance when the battery pack is mounted on a vehicle, or may be stored in the mounting space. This may cause inconveniences such as leaving an extra gap. Alternatively, there may be a design disadvantage in that the tolerance of the outer size guarantee value of the assembled battery is increased to allow the variation in the outer size (that is, an extra space is provided around the assembled battery). Therefore, in manufacturing the assembled battery, it is desirable to reduce the variation in the length in the arrangement direction.

  The present invention was developed in order to solve the above-mentioned problems relating to the construction of a conventional assembled battery, and its object is to make the shape of the electrode body accommodated inside each unit cell constituting the assembled battery uneven. Accurate size as set in advance by suppressing variations in the length of the assembled battery in the arrangement direction (particularly, the length dimension of the assembled battery in the arrangement direction of the unit cells constituting the assembled battery) It is to provide a method capable of manufacturing an assembled battery having:

  According to the present invention, there is provided a method of manufacturing an assembled battery in which a predetermined number of cells are arranged in a predetermined direction and constrained under a load applied in the arrangement direction. The method includes a step of preparing a plurality of unit cells each including an electrode body having a positive electrode and a negative electrode, and a container accommodating the electrode body. The method also includes a step of classifying the plurality of unit cells into a plurality of thickness ranks according to the thickness of the electrode bodies housed in the unit cells in the arrangement direction. The method also includes the step of constructing an assembled battery by arranging a predetermined number of the unit cells in the arrangement direction and restraining the cells in a state in which a load is applied in the arrangement direction. Here, in the assembled battery construction step, the assembled battery is selected by combining a predetermined number of unit cells used in the construction of the assembled battery from two or more thickness ranks of the plurality of classified thickness ranks. Is performed so that the length in the arrangement direction conforms to a preset specified length.

  In the present specification, the term “unit cell” is a term that refers to individual storage elements that can be connected in series to each other to form an assembled battery, and includes batteries and capacitors of various compositions unless otherwise specified. The term "secondary battery" generally means a battery that can be repeatedly charged, and includes so-called storage batteries such as lithium-ion secondary batteries and nickel-hydrogen batteries. The electric storage element that constitutes the lithium-ion secondary battery is a typical example included in the “single battery” here, and a lithium-ion secondary battery module including a plurality of such single batteries is disclosed here. It is a typical example of a "battery pack". The technology disclosed herein arranges a predetermined number of flat cells (for example, a lithium ion secondary battery) having a flat outer shape in a stacking direction (stacking direction) of the flat surfaces, and electrode terminals of those single cells. Can be particularly preferably applied to an assembled battery formed by connecting in series or in parallel.

  According to the assembled battery manufacturing method of the above configuration, the predetermined number of cells used for constructing the assembled battery cancels out the variation in the thickness of the electrode body in each cell (and thus the variation in the thickness of each cell in the restrained state). Since the length of the assembled battery in the arrangement direction is selected and combined so as to conform to the specified length, an accurate size (especially, the length of the assembled battery with respect to the arrangement direction of the unit cells constituting the assembled battery is It is possible to manufacture an assembled battery having a specific size. Therefore, according to the manufacturing method of the present invention, it is possible to provide an assembled battery for vehicle use and other purposes, which has a good outer size (length in the arrangement direction) and is easy to mount.

In a preferred embodiment of the method for manufacturing an assembled battery disclosed herein, the electrode body includes a positive electrode sheet having a positive electrode active material layer on a long positive electrode current collector, and a negative electrode active material on a long negative electrode current collector. A flat wound electrode body is obtained by winding a negative electrode sheet having a material layer.
The thickness of the wound electrode body tends to be uneven depending on the winding degree and state. Therefore, in a unit cell including such a wound electrode body, the thickness of the unit cell tends to be nonuniform when restrained. In the manufacturing method with the above configuration, the length of the assembled battery in the array direction conforms to the reference length. By selecting and combining the unit cells having different thickness ranks, it is possible to manufacture an assembled battery in which the length of the assembled battery in the arrangement direction is accurately matched with the specified value (specified length). Therefore, according to the manufacturing method of the present aspect, it is possible to manufacture an assembled battery including a plurality of unit cells each including the wound electrode body as a constituent element and having excellent mountability.

  In a preferred aspect of the assembled battery manufacturing method disclosed herein, in the step of preparing a plurality of the single cells, a positive electrode active material layer having a length corresponding to a plurality of the single cells is provided on the positive electrode current collector. A positive electrode sheet base material continuously formed in the longitudinal direction, and a negative electrode sheet in which a negative electrode active material layer having a length corresponding to a plurality of unit cells is continuously formed on the negative electrode current collector in the longitudinal direction. A process of forming a plurality of wound electrode bodies by cutting the base material in a predetermined length while overlapping and winding the base material is included. According to such a configuration, while a plurality of wound electrode bodies can be efficiently formed, the shape of the obtained wound electrode body is likely to be irregular. However, according to the manufacturing method of the above configuration, the variation in length in the arrangement direction of the battery pack, which may occur due to the uneven shape of the wound electrode body, is suppressed, and the accurate size is set as preset. An assembled battery can be manufactured. Therefore, according to the manufacturing method of the present aspect, it is possible to efficiently manufacture an assembled battery having a good outer size and good mountability.

  In a preferred embodiment of the method for manufacturing an assembled battery disclosed herein, the number of cells constituting the assembled battery is 30 or more (preferably 50 or more). As the number of unit cells increases, the capacity of the battery pack is increased, and the length of the battery pack in the arrangement direction tends to vary due to the uneven shape of the electrode bodies. However, according to the manufacturing method of the above configuration, despite the variation in the thickness of the electrode body in a large number of cells, the variation in the thickness of the electrode body in each cell is canceled out and the length in the arrangement direction is set to the specified value. It is possible to manufacture an assembled battery that accurately matches the (specified length). Therefore, according to the manufacturing method of this aspect, it is possible to manufacture an assembled battery having a high capacity and good mountability.

It is a perspective view which shows the structure of the assembled battery which concerns on one Embodiment typically. It is a side view which shows typically the structure of the assembled battery which concerns on one Embodiment. It is a front view which shows typically the wound electrode body which concerns on one Embodiment. It is a figure which shows typically the state in the container of the single cell which concerns on one Embodiment. It is explanatory drawing which shows typically the manufacturing method of the wound electrode body which concerns on one Embodiment. It is explanatory drawing which shows typically the manufacturing method of the wound electrode body which concerns on one Embodiment. It is a graph which shows the relationship between the thickness of an electrode body and the thickness of the unit cell in a restrained state.

Hereinafter, preferred embodiments of the present invention will be described. It should be noted that matters other than matters particularly referred to in the present specification (for example, the structure of the unit cell which is a constituent element of the assembled battery) and matters necessary for carrying out the present invention (for example, configurations of the positive electrode, the negative electrode, and the separator). The manufacturing method, the method for restraining the unit cells, and the method for mounting the assembled battery on the vehicle) can be understood as a design item for those skilled in the art based on the conventional technology in the field. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the field.
The assembled battery according to the present invention can be suitably used as a power source for a motor (electric motor) mounted on a vehicle such as an automobile. Therefore, the present invention provides a vehicle (typically an automobile, particularly an automobile including an electric motor such as a hybrid vehicle, an electric vehicle, a fuel cell vehicle) including the assembled battery as a power source.

  An assembled battery manufactured by applying the technique disclosed herein is an assembled battery in which unit cells (typically, unit cells having a flat outer shape) are arrayed and constrained in the array direction (stacking direction). As long as it is a battery, the structure of each unit cell is not particularly limited. Examples of suitable single cells to which the present invention is applied include secondary batteries such as nickel hydrogen batteries and electric double layer capacitors. Above all, the present invention can be preferably employed as a method for producing an assembled battery including a lithium ion secondary battery as a single battery. Since the lithium-ion secondary battery is a secondary battery that can realize high output with high energy density, it is possible to construct a high-performance assembled battery, especially a vehicle-mounted assembled battery (battery module). Further, the present invention is suitable as a method for manufacturing an assembled battery in a form in which a plurality of the arranged unit cells are connected in series or in parallel (typically in series).

  Although not intended to be particularly limited, the following is an example of a case where a flat-shaped lithium ion secondary battery is used as a unit cell and a battery pack including a plurality of the unit cells connected in series is manufactured. The invention will be described in detail. Further, in the following drawings, members / sites having the same function are denoted by the same reference numerals, and redundant description may be omitted or simplified.

  A unit cell used as a constituent element of an assembled battery manufactured in the embodiment shown below is typically a predetermined battery constituent material (active material for each of positive and negative electrodes), like the unit cell equipped in a conventional assembled battery. , A collector for each of positive and negative electrodes, a separator, etc.) and a container for accommodating the electrode body and a suitable electrolyte.

  As shown in FIG. 1 and FIG. 2 as an example, the battery pack 10 disclosed herein includes a plurality (typically 10 or more (for example, 10 to 100), preferably 30 or more, and more preferably 50. As described above, more preferably 60 or more). The unit cell 12 includes a container 14 having a shape (a box shape in the present embodiment) capable of accommodating a flat wound electrode body described later.

The container 14 is provided with a positive electrode terminal 15 electrically connected to the positive electrode of the wound electrode body and a negative electrode terminal 16 electrically connected to the negative electrode of the electrode body. As shown in the drawing, one positive electrode terminal 15 and the other negative electrode terminal 16 are electrically connected to each other between the adjacent unit cells 12 by a connector 17. By connecting the unit cells 12 in series in this manner, the assembled battery 10 having a desired voltage is constructed.
Note that these containers 14 may be provided with safety valves and the like for venting gas generated inside the containers, as in the case of conventional single cell containers. Since the configuration of the container 14 itself does not characterize the present invention, detailed description thereof will be omitted.

  The material of the container 14 is not particularly limited as long as it is the same as that used in the conventional unit cell. From the viewpoint of being suitable for mounting on a vehicle or the like, as a material suitable for carrying out the present invention, a relatively lightweight material can be mentioned. For example, a container made of a metal (for example, aluminum or steel), a synthetic resin (for example, a polyolefin resin such as polyethylene or polypropylene, or a high melting point resin such as polyethylene terephthalate, polytetrafluoroethylene, or a polyamide resin) is preferable. Can be used. Alternatively, a resin film container that has been conventionally used as an outer casing of a battery, for example, an outer surface (protection) layer made of a high melting point resin (for example, a high melting point resin such as polyethylene terephthalate, polytetrafluoroethylene, polyamide resin) , A barrier layer composed of a metal foil (for example, aluminum or steel) (that is, a layer capable of blocking gas and moisture), and a heat-fusible resin (a resin having a relatively low melting point, for example, ethylene vinyl acetate, or polyethylene, It may be a container made of a laminated film having a three-layer structure with an adhesive layer composed of a polyolefin resin such as polypropylene). The container 14 according to the present embodiment is made of aluminum, for example.

  As shown in FIGS. 1 and 2, the plurality of unit cells 12 are reversed one by one such that the positive electrode terminals 15 and the negative electrode terminals 16 are alternately arranged at regular intervals, and the wide surface of the container 14 is inverted. 14A (that is, a surface corresponding to a flat surface of a wound electrode body 30 to be described later that is housed in the container 14) are arranged in opposite directions. Further, the cooling plates 11 having a predetermined shape are arranged in close contact with the wide surface 14 </ b> A of the container 14 between the arranged unit cells 12 and both outsides in the unit cell arrangement direction. The cooling plate 11 functions as a heat dissipation member for efficiently dissipating heat generated in each unit cell during use, and introduces a cooling fluid (typically air) between the unit cells 12. It has a possible frame shape (for example, a concavo-convex shape when viewed from the side like a comb shape shown). A cooling plate 11 made of metal having good thermal conductivity or made of lightweight and hard polypropylene or other synthetic resin is suitable.

  A pair of end plates 18 and 19 are arranged further outside the cooling plates 11 arranged on both outsides of the arrayed unit cells 12 and cooling plate 11. The unit cell group and the end plates 18, 19 as a whole are stacked in a stacking direction of the constrained body 24 by a plurality of tightening restraint bands 21 attached so as to bridge (connect) both end plates 18, 19. It is constrained with a load applied in the (arrangement direction).

Then, the entire unit cells arranged in the stacking direction of the unit cells 12, the cooling plate 11, and the end plates 18 and 19 (hereinafter also referred to as “constrained body”) form the end plates 18 and 19. The restraint band 21 for tightening, which is attached so as to crosslink, restrains the restrained body at a prescribed restraining pressure P in the stacking direction. More specifically, as shown in FIG. 2, by fastening and fixing the end portion of the restraint band 21 to the end plate 18 with the screw 22, the restrained body 24 has a restraining pressure P (for example, a container) defined in the arrangement direction. The surface pressure that the wall surface of 14 receives is about 2 × 10 ^{6 to} 5 × 10 ⁶ Pa). The length in the arrangement direction of the battery pack 10 that is restrained by the prescribed restraint pressure P (the length between the outer ends of the end plates 18, 19 in the example shown in FIGS. 1 and 2) is the prescribed length LT. Here, in the present specification, the “specified length LT” refers to the length of the battery pack along the arrangement direction of a predetermined number of unit cells that form the battery pack, and is typically allowed including tolerances. It can be understood as a range of length. For example, when the specified length LT is X cm, it can be grasped as a range of X ± α including the tolerance ± α.

In the manufacturing method according to the present example, the assembled battery 10 having the above configuration is efficiently manufactured as described below so that the specified length LT is stably realized. Hereinafter, the manufacturing method will be described with reference to the schematic diagrams shown in FIGS.
First, a process of preparing a plurality of unit cells 12 used to construct the assembled battery 10 will be described. The unit cell 12 includes an electrode body 30 having a positive electrode and a negative electrode. In this embodiment, the electrode body 30 includes a positive electrode sheet 32 including a positive electrode active material layer on a long positive electrode current collector, a negative electrode sheet 34 including a negative electrode active material layer on a long negative electrode current collector, and a separator. 36 is a flat wound electrode body 30.

The material and the members themselves constituting the wound electrode body 30 may be the same as those of the electrode body of the conventional lithium ion battery and are not particularly limited. For example, the positive electrode sheet 32 may be formed by providing a positive electrode active material layer for a lithium ion battery on a long positive electrode current collector. Aluminum foil (this embodiment) and other metal foils suitable for the positive electrode are preferably used for the positive electrode current collector. As the positive electrode active material, one or more materials conventionally used in lithium ion batteries can be used without particular limitation. Suitable examples include lithium transition metal oxides such as LiMn ₂ O ₄ , LiCoO ₂ , and LiNiO ₂ . For example, an aluminum foil having a length of 2 m to 4 m (for example, 2.7 m), a width of 8 cm to 12 cm (for example, 10 cm) and a thickness of 5 μm to 20 μm (for example, 15 μm) is used as a current collector, and a positive electrode is provided in a predetermined region on the surface thereof. By forming the active material layer, the suitable positive electrode sheet 32 is obtained.

  On the other hand, the negative electrode sheet 34 may be formed by providing a negative electrode active material layer for a lithium ion battery on a long negative electrode current collector. For the negative electrode current collector, a copper foil (in this embodiment) or another metal foil suitable for a negative electrode is preferably used. As the negative electrode active material, one or more materials conventionally used in lithium ion batteries can be used without particular limitation. Suitable examples include carbonaceous materials such as graphite carbon and amorphous carbon, lithium transition metal oxides and transition metal nitrides. For example, a copper foil having a length of 2 m to 4 m (for example, 2.9 m), a width of 8 cm to 12 cm (for example, 10 cm), and a thickness of 5 μm to 20 μm (for example, 10 μm) is used, and a negative electrode active material layer is provided in a predetermined region on the surface thereof. A suitable negative electrode sheet 34 is obtained by forming.

  Further, as a suitable separator sheet 36 used between the positive and negative electrode sheets 32 and 34, one made of a porous polyolefin resin is exemplified. For example, a porous separator sheet made of synthetic resin (for example, polyolefin such as polyethylene) having a length of 2 m to 4 m (for example, 3.1 m), a width of 8 cm to 12 cm (for example, 11 cm) and a thickness of 5 μm to 30 μm (for example, 25 μm) is used. It can be preferably used.

  When constructing the spirally wound electrode body 30, the positive electrode sheet 32, the first separator 36, the negative electrode sheet 34, and the second separator 36 are constructed in the same manner as in the ordinary spirally wound electrode body of a lithium ion secondary battery. Are laminated in this order, and the positive electrode sheet 32 and the negative electrode sheet 34 are wound while being slightly displaced. Then, the flat wound electrode body 30 is manufactured by crushing the obtained wound body from the side surface and squeezing it.

In a preferred embodiment, when manufacturing the wound electrode body 30, a positive electrode active material layer is formed on a long positive electrode current collector to prepare a positive electrode sheet. For example, as shown in FIG. 5, a composition obtained by dispersing a material for forming a positive electrode active material containing a positive electrode active material as a main component in an appropriate dispersion medium has one end portion in the longitudinal direction of the positive electrode current collector (application starting point). From one end to the other end (application end point), and by sandwiching this between rollers 68 and pressing it, it is equivalent to a plurality (eg 100 to 500) of cells 12 on the positive electrode current collector. A positive electrode sheet base material 32a having a length of a positive electrode active material layer continuously formed in the longitudinal direction is prepared.
Similarly, a composition in which a material for forming a negative electrode active material containing a negative electrode active material as a main component is dispersed in a suitable dispersion medium is applied from one end (application starting point) to the other end (application start point) in the longitudinal direction of the negative electrode current collector. By applying and drying at the application end point) and sandwiching it between rollers and pressing it, a length corresponding to a plurality (for example, 100 to 500) of the single cells 12 is provided on the long negative electrode current collector. A negative electrode sheet base material 34a in which the negative electrode active material layer is continuously formed in the longitudinal direction is produced.

  Then, as shown in FIG. 6, a positive electrode roll 33 in which the positive electrode sheet base material 32a is wound in a roll shape, a negative electrode roll 35 in which the negative electrode sheet base material 34a is wound in a roll shape, and a separator roll (of the unit cell 12) (A separator sheet base material 36a having a length corresponding to a plurality of pieces is wound in a roll shape) 37 is set in a winding device, and each of the rolls 33, 35 and 37 is set to a positive electrode sheet base material 32a and a negative electrode sheet base material. The material 34a and the two separator sheet base materials 36a are pulled out. Then, the positive electrode sheet base material 32a, the first separator sheet base material 36a, the negative electrode sheet base material 34a, and the second separator sheet base material 36a are laminated in this order and wound up by a predetermined amount. The wound electrode body 30 is manufactured by cutting at a terminal position so as to have a predetermined length (a length corresponding to one unit cell), and winding the winding end portion cut at the terminal position. By repeating this step, a plurality of (for example, 100 to 500) wound electrode bodies 30 can be continuously formed from one roll 33, 35, 37.

As shown in FIG. 3, the obtained flat-shaped wound electrode body 30 has a positive electrode sheet 32 and a negative electrode as a result of being wound while being slightly displaced in the lateral direction with respect to the winding direction of the wound electrode body 30. A part of the end of the sheet 34 is a wound core portion 31 (that is, a portion in which the positive electrode active material layer forming portion of the positive electrode sheet 32, the negative electrode active material layer forming portion of the negative electrode sheet 34, and the separator sheet 36 are densely wound. ) From the outside. A positive electrode lead terminal 32B and a negative electrode lead terminal 34B are attached to the positive electrode side protruding portion (that is, a portion where the positive electrode active material layer is not formed) 32A and the negative electrode side protruding portion (that is, a portion where the negative electrode active material layer is not formed) 34A. The lead terminals 32B and 34B are electrically connected to the positive electrode terminal 15 and the negative electrode terminal 16, respectively. Then, as shown in FIG. 4, the wound electrode body 30 is housed in the container 14 with the winding axis lying sideways, and an appropriate amount of supporting salt (for example, lithium salt such as LiPF ₆ ) is added in an appropriate amount. The unit cell 12 is constructed by injecting and sealing a non-aqueous electrolyte (electrolyte solution) such as a mixed solvent of diethyl carbonate and ethylene carbonate (for example, a concentration of 1 M) (for example, a mass ratio of 1: 1). After that, by repeating charging and discharging once or a plurality of times for each unit cell 12, the assembled unit cell can be activated and put into a state in which it can be actually used.

Here, according to the knowledge obtained by the present inventor, as described above, when a plurality of unit cells 12 are arrayed and constrained in the array direction in manufacturing the assembled battery 10, the container 14 is flexible. Therefore, the container 14 may be distorted or deformed in the load direction. Therefore, the thickness of each unit cell 12 in the arrangement direction in a state of being constrained by applying a load in a predetermined arrangement direction depends largely on the thickness of the electrode body 30 inside the container 14 rather than the outer shape of the container 14 in the unconstrained state. To do.
However, in general, the thickness of the electrode body 30 has some variation (unevenness) due to fluctuations in conditions during manufacturing.
When a large number of unit cells 12 having the electrode bodies 30 having variations in thickness are arranged and constrained in the stacking direction as described above, as shown in FIG. 7, each unit cell is caused by variations in the thickness of the electrode bodies 30. Variations in the thickness of the cells 12 in the arrangement direction occur, and variations in the thickness of the unit cells 12 are accumulated. As a result, the length of the obtained battery pack 10 in the arrangement direction varies. FIG. 7 is a graph showing the relationship between the thickness of the electrode body and the thickness (when restrained) of the unit cell including the electrode body.

  In the manufacturing method disclosed herein, in order to converge variations in the length of the assembled battery 10 in the arrangement direction, which may occur due to the uneven shape of the electrode bodies 30, the electrodes within each unit cell 12 are converged. The assembled battery 10 is constructed by combining a plurality of unit cells 12 in which variations in the thickness of the body 30 are offset.

That is, the step of preparing a plurality of the unit cells 12 described above includes measuring the thickness T of the electrode bodies 30 housed in each unit cell 12 in the arrangement direction.
Then, according to the thickness (measured value) T of the electrode body 30 in the arrangement direction, each of the plurality of unit cells 12 is classified into a plurality of thickness ranks having different thickness ranges (range) (classification step). For example, based on the graph of FIG. 7, the electrode body 30 in which the thickness T of the electrode body 30 in the arrangement direction is in the range of the target electrode body thickness A ± 0.2 mm (A−0.2 mm ≦ T ≦ A + 0.2 mm) , "A" is a representative value, and the thickness T of the electrode body 30 in the arrangement direction is in the range of A + 0.2 mm <T≤A + 0.6 mm, the representative value is "A + 0.4 mm". The electrode body 30 having a thickness rank 1 in which the thickness T in the arrangement direction of the electrode body 30 is in the range of A-0.6 mm ≦ T <A-0.2 mm has “A-0.4 mm” as a representative value. The thickness is classified into rank 3. Then, a predetermined number of unit cells 12 used for constructing the assembled battery 10 are defined lengths in which the length of the assembled battery 10 in the arrangement direction is preset from two or more thickness ranks of the above-mentioned thickness ranks 1 to 3. Select a combination that matches the LT.

  In a preferred embodiment, a predetermined number of unit cells 12 used to construct the assembled battery 10 are combined from the above-mentioned thickness ranks 1 to 3 such that the sum of the representative values of the thickness ranks to which each unit cell belongs is the specified electrode body length RT. Select with. Specifically, when selecting and combining X cells of thickness rank 1, Y cells of thickness rank 2, and Z cells of thickness rank 3, when selecting and combining, “A + 0.4 mm” × X + A × Y + The combination is selected such that the total value of “A−0.4 mm” × Z matches the specified electrode body length RT. The specified electrode body length RT is typically calculated from “target electrode body thickness A × predetermined number” and has a total thickness of the specified electrode body length RT and other constituent members of the assembled battery. It is set so that the assembled battery having the specified length LT in the arrangement direction is configured by restricting the body 24 with the specified restriction pressure P.

  The predetermined number of unit cells 12 selected above are arranged alternately with the cooling plates 11, and further the end plates 18 and 19 are arranged at both ends to construct the restrained body. Then, as shown in FIG. 2, the ends of the restraint band 21 are tightened and fixed to the end plates 18 and 19 with screws 22, so that the restrained bodies 24 are restrained so that a prescribed restraining pressure P is applied in the arrangement direction. Then, the assembled battery 10 is constructed (assembly battery constructing step).

Here, according to the manufacturing method of the present embodiment, the predetermined number of the unit cells 12 to be used are the electrode units 30 in each unit cell 12 despite the variation in the thickness of the electrode unit 30 in each unit cell 12. Of two or more thickness ranks 1 to 1 so that the variation in the thickness of the battery pack (and thus the variation in the thickness of each unit cell in the restrained state) is canceled so that the length in the arrangement direction of the battery pack 10 conforms to the specified length LT. It is selected from 3 and combined. As a result, variations in the thickness of the individual electrode bodies can be offset, and the assembled battery 10 whose length in the arrangement direction satisfies the specified length LT can be manufactured.
Therefore, as in the case of a conventional battery pack, when the length of the battery pack in the array direction varies due to the uneven shape of the electrode bodies in each battery cell, the mounting space prepared in advance can be used. It is possible to avoid the inconvenience that the assembled battery does not fit, or an extra gap remains when the assembled battery fits in the mounting space. In addition, since it is not necessary to make a large tolerance for the guaranteed outer dimensions of the assembled battery (that is, an extra space is provided around the assembled battery) to allow the variation in the outer size of the assembled battery, the mounting space for the assembled battery 10 can be reduced. It can be designed smaller than before. Furthermore, for example, only the cells 12 corresponding to the thickness rank 2 are used for manufacturing the assembled battery 10, and the cells 12 corresponding to the thickness rank 1 (thick) or the thickness rank 3 (thin) are excluded as defective products. Compared with the above, the manufacturing method according to the present embodiment can reduce the defective rate of the unit cell 12 and reduce the manufacturing cost of the assembled battery 10.

A preferred application target of the technology disclosed herein is an assembled battery including the wound electrode body 30 formed by using the positive electrode sheet base material 32a and the negative electrode sheet base material 34a described above. While such a wound electrode body 30 can be efficiently formed, its shape tends to be irregular. More specifically, in the positive electrode sheet base material 32a (FIG. 5) in which a positive electrode active material layer having a length corresponding to a plurality of unit cells is continuously formed on the positive electrode current collector, The thickness of the positive electrode active material layer tends to gradually decrease from one end (application start point) to the other end (application end point) in the longitudinal direction. Similarly, in the negative electrode sheet base material 34a in which a negative electrode active material layer having a length corresponding to a plurality of unit cells 12 is continuously formed on the negative electrode collector, one end in the longitudinal direction of the negative electrode collector is formed. The thickness of the negative electrode active material layer tends to gradually decrease from the part (application start point) to the other end (application end point). Therefore, as shown in FIG. 6, when a plurality of wound electrode bodies 30 are continuously formed using the positive electrode sheet base material 32a and the negative electrode sheet base material 34a, the positive electrode sheet base material 32a and the negative electrode sheet base material 34a become Since the thickness variations have the same tendency, the thick portions (or thin portions) of the both are combined, and the thickness difference of the wound electrode body 30 is likely to be large. Further, in the initial stage of winding, the relatively thick wound electrode body 30 tends to solidify, and in the latter stage of winding, the relatively thin wound electrode body 30 tends to solidify.
When the assembled battery is constructed by combining the unit cells having the relatively thick wound electrode body 30 (or the relatively thin wound electrode body 30) solidified in such an order of formation, the length of the assembled battery in the arrangement direction is increased. The variation in depth tends to be particularly large.
However, according to this aspect, it is possible to suppress the variation in the length of the assembled battery in the arrangement direction which may occur due to the irregular shape of the wound electrode body, and to provide an assembled battery having an accurate size as preset. It can be manufactured. Therefore, according to the manufacturing method of the present aspect, it is possible to efficiently manufacture an assembled battery having a good outer size and good mountability.

  In the above-described embodiment, the case where the plurality of unit cells 12 are classified into three thickness ranks 1 to 3 according to the thickness of the electrode body 30 is illustrated, but the number of classified thickness ranks is not limited to this. For example, the number of thickness ranks may be two or more, may be three or more, or may be five or more. The upper limit of the number of thickness ranks is not particularly limited as long as the above effects can be obtained, but may be 10 or less, for example.

  Further, in the above-described embodiment, the thickness of the electrode body 30 in the arrangement direction is measured and the plurality of thickness ranks are classified based on the measured values, but the criterion for classification is not limited to the actually measured values. For example, the sheet thickness of the positive electrode sheet 32 and the negative electrode sheet 34 used for manufacturing the electrode body 30 may be measured, and the thickness of the electrode body 30 may be estimated from the sheet thickness. Since the thickness of the electrode body 30 depends on the thicknesses of the positive electrode sheet 32 and the negative electrode sheet 34, the thickness of the electrode body 30 may be estimated from the sheet thickness and classified into a plurality of thickness ranks based on the estimated value. However, as in the above-described embodiment, the classification into a plurality of thickness ranks based on the actual measurement value of the thickness of the electrode body 30 allows the classification to be performed more accurately and conforms to the prescribed arrangement direction length LT. The assembled battery 10 can be manufactured accurately.

  Further, in the above-described embodiment, the case where all the thicknesses (total number) of the individual electrode bodies 30 are measured in the step of preparing a plurality of unit cells 12 has been exemplified, but the number of electrode bodies 30 whose thickness is to be measured is It is not limited to this. For example, the thickness of each electrode body 30 may be grasped by sampling extraction for each lot. For example, when a plurality of wound electrode bodies 30 are continuously formed using one positive electrode sheet base material 32a and one negative electrode sheet base material 34a as described above, the distribution of the thickness of the wound electrode body 30 is irregular ( Rather than being random, the relatively thick wound electrode body 30 tends to solidify in the initial winding stage, and the relatively thin wound electrode body 30 tends to solidify in the late winding stage. Therefore, in the process of preparing a plurality of unit cells 12, even if the total thickness of the individual electrode bodies 30 is not measured, sampling of each of the plurality of wound electrode bodies that are solidified in the order of formation is performed by sampling and extracting the individual electrode bodies 30. The approximate thickness can be grasped, and each lot can be classified into a plurality of thickness ranks. Such a mode may be included in the assembled battery manufacturing method disclosed herein.

Although the preferred embodiments of the method for manufacturing a battery pack of the present invention have been described above in detail, the present invention is not intended to be limited to these specific embodiments.
For example, in the above-described embodiment, the electrode body 30 is housed in the container 14 in such a direction that the winding axis of the wound electrode body 30 is the width direction of the unit cell 12 (thickness direction of the paper surface in FIG. 2). The electrode body 30 may be arranged so that the axis of rotation is in the height direction of the unit cell 12 (the vertical direction in FIG. 2). Instead of the wound type electrode body 30, a laminated type electrode body formed by alternately laminating a plurality of positive electrode sheets and a plurality of negative electrode sheets together with a separator sheet may be used. Even in the laminated type electrode body, variation in thickness (unevenness) may occur due to a change in conditions during manufacturing. The invention disclosed herein is directed to a unit cell in which electrode bodies having various configurations are housed in a container (particularly, a wound-type or laminated-type electrode body, in which the sheets constituting the electrode body are laminated units). It can be preferably applied to an assembled battery formed by arranging a plurality of unit cells each of which is housed in a container in a direction overlapping with each other in the stacking direction.

Further, the type of the unit cells that form the assembled battery is not limited to the above-mentioned lithium ion secondary battery, but batteries of various contents having different electrode body constituent materials and electrolytes, such as lithium secondary batteries having lithium metal or lithium alloy as the negative electrode. It may be a battery, a nickel hydrogen battery, a nickel cadmium battery, or an electric double layer capacitor.
The battery pack 10 shown in FIG. 1 has a simple structure in order to explain the present invention. However, various modifications and additions of equipment can be made without impairing the structure and effects of the present invention. It will be obvious to the trader. For example, when mounted on a vehicle such as an automobile, an outer cover for protecting a main part of the battery pack (such as a unit cell group), a component for fixing the battery pack to a predetermined portion of the vehicle, and a plurality of battery packs ( Parts for connecting the battery modules) to each other may be equipped, but the presence or absence of such equipment does not affect the technical scope of the present invention.

10 assembled battery 11 cooling plate 12 unit cell 14 container 15 positive electrode terminal 16 negative electrode terminal 17 connection tool 18, 19 end plate 21 restraining band 30 wound electrode body 32 positive electrode sheet 34 negative electrode sheet 36 separator

Claims (3)

A method for producing an assembled battery in which a predetermined number of unit cells are arranged in a predetermined direction and restrained in a state in which a load is applied in the arrangement direction,
A step of preparing a plurality of unit cells each including an electrode body having a positive electrode and a negative electrode, and a container accommodating the electrode body;
A step of classifying the plurality of unit cells into a plurality of thickness ranks according to the thickness in the arrangement direction of the electrode bodies housed in the unit cells;
Constructing an assembled battery by arranging a predetermined number of the unit cells in the arrangement direction and constraining them in a state in which a load is applied in the arrangement direction;
Including
In the assembling step of the assembled battery, the array of the assembled battery is performed by selecting and combining a predetermined number of unit cells used for constructing the assembled battery from two or more thickness ranks of the classified plurality of thickness ranks. A method of manufacturing an assembled battery, which is performed so that the length in a direction matches a preset specified length.   The electrode body has a flat shape formed by winding a positive electrode sheet having a positive electrode active material layer on a long positive electrode current collector and a negative electrode sheet having a negative electrode active material layer on a long negative electrode current collector. The manufacturing method according to claim 1, which is the wound electrode body.   In the step of preparing a plurality of the unit cells, a positive electrode sheet base material on which a positive electrode active material layer having a length corresponding to a plurality of unit cells is continuously formed in the longitudinal direction on the positive electrode current collector, While winding the negative electrode sheet base material on which the negative electrode active material layer having a length corresponding to a plurality of unit cells is continuously formed in the longitudinal direction on the negative electrode current collector, each predetermined length The manufacturing method according to claim 2, further comprising a treatment of forming a plurality of wound electrode bodies by cutting into a plurality of pieces.